In addition to higher performance of products for bleaching or coloring hair, consumers of such products are more and more sensitive to the usage quality of the products. From the viewpoint of usage quality, the following, for example, can be regarded as major drawbacks: malodor from ammonia which is typically contained as an alkaline agent in conventional hair bleaching or coloring products; difficulty in handling conventional hair bleaching or coloring products which are in the form of a liquid, gel or cream; and the like.
In order to reduce the problems occurring with the pungent odor of ammonia, it has been proposed to replace totally or partially ammonia with another alkaline agent such as alkanolamine (e.g., monoethanolamine and aminomethylpropanol). However, this modification tends to result in a decrease of the bleaching or coloring efficiency. Also, such non-ammonia type alkaline agents are generally concerned about scalp irritation. Therefore, ammonia still maintains a prominent position as an active alkaline ingredient for hair color.
As an alternative hair bleaching or coloring composition based on ammonia as an alkaline agent, JP-A-2002-226342 discloses an emulsion including emulsified particles with a sufficiently small size such as 10 μm or less, wherein the emulsion is believed to inhibit ammonia odor.
JP-A-2002-226342 discloses that it is possible to control emulsion size by optimizing at least one or two factors selected from: the composition of the emulsion, order of blending and/or agitation level. However, generally, it is necessary to use, for example, special emulsification equipment to make an emulsion including emulsified particles of micron size, and they are not industrially economical. Therefore, efficient and economical malodor reducing technology for a composition for keratin fibers such as hair including an ammonia-based alkaline agent has been required.